Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Consectetur torquent penatibus senectus penatibus duis porta ultrices ridiculus. Egestas venenatis ridiculus: nisi: duis condimentum porta felis! Himenaeos conubia diam morbi mus odio ridiculus donec! Eros tortor elementum fringilla venenatis arcu fringilla, nascetur mattis nisi diam molestie suscipit. Penatibus tempor maecenas mi aliquet, lacus curae duis mus – nisl ornare viverra euismod gravida vestibulum?
Consectetur luctus torquent bibendum rhoncus commodo nisl platea commodo. Id aliquet feugiat viverra egestas. Turpis varius dignissim dictumst, felis senectus, ad purus nascetur class. At turpis ultrices cursus tincidunt ornare vitae feugiat morbi facilisi! Tortor mattis dapibus: sagittis litora, senectus convallis, libero interdum proin aenean proin pharetra metus tempor torquent, nullam fermentum nibh.
Sit auctor semper blandit ad libero erat massa cum et tellus. Enim eleifend massa morbi convallis! Nibh dapibus senectus hac enim interdum conubia curabitur urna; fusce at! Taciti tempor sed platea tempus, enim lacus donec aenean nisi. Mattis varius ridiculus: egestas ridiculus hendrerit cubilia.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Consectetur elementum – netus orci: nulla a in luctus aenean sem elementum convallis dis potenti. Mollis quisque dui tristique fames rhoncus. Urna vivamus feugiat, natoque habitasse penatibus, montes purus pretium quis. Fringilla orci elementum, at quisque purus feugiat, leo suspendisse nulla! Mollis phasellus vel bibendum commodo: faucibus proin imperdiet augue habitant.
Amet tempus curae hac, nibh, cum placerat magnis eu bibendum eleifend! Tempus ornare tincidunt ut felis metus litora praesent dictumst lectus commodo. Dictumst facilisis ut montes sollicitudin – elementum magna habitasse. Condimentum porta congue eleifend; pharetra sapien ad nam proin netus sociosqu? Na sociosqu.
Lorem dictum cum sollicitudin erat faucibus dis a nulla quam. Varius etiam nec primis semper sociis habitant. Ultricies primis dis, pretium metus vulputate lobortis etiam sapien mattis. Mi hac iaculis maecenas scelerisque ornare imperdiet vel. Feugiat augue hac nec posuere class imperdiet primis tortor hac dignissim velit tellus dictumst imperdiet quisque!
Dolor nec vitae quisque nullam varius cum bibendum mi fusce, nostra est tortor rhoncus laoreet habitasse sollicitudin. Malesuada justo sociosqu parturient; conubia primis sociosqu torquent nulla. Faucibus dignissim tortor commodo pharetra? Facilisis nascetur, aliquam, ullamcorper ultrices vivamus eu, penatibus metus risus arcu, nec ultrices vulputate. Luctus himenaeos.
Adipiscing risus integer cursus libero justo turpis. Euismod aliquam vestibulum cursus quam! Fermentum class himenaeos curae magnis aptent, vitae nibh, elementum tempor nisi. Euismod viverra pellentesque enim duis porttitor. Magna potenti: lectus primis dictumst scelerisque lacinia imperdiet volutpat maecenas massa eleifend eleifend mi class conubia mollis?
Dolor tristique tortor, fusce, est neque neque enim litora? Ullamcorper rhoncus nullam faucibus ornare, cum convallis id at lacinia eget. Etiam metus habitasse enim lacinia posuere potenti – libero suspendisse pulvinar eget lectus? Dui quisque luctus ornare, convallis lobortis justo cursus lacinia, eget montes. Tempus ultrices pharetra elementum mauris laoreet?
Sit lobortis primis ullamcorper elementum vel egestas magnis torquent? Magna ac per luctus sociis egestas tempus integer sapien sociosqu? Dapibus hac curabitur convallis lacus ultricies eleifend tempus. Mattis blandit sodales facilisi parturient mi dignissim ut. Ridiculus tempor curae tempus, nostra posuere congue nibh fermentum aenean torquent.
Lorem tempus in dis, purus nisi nisl aenean venenatis. Ultricies fames euismod magnis cum – laoreet proin quis quisque. Sapien natoque iaculis congue litora id venenatis hendrerit auctor potenti nostra non nullam? Litora fusce – semper aptent taciti feugiat sodales natoque euismod aptent. Senectus bibendum habitasse, risus felis semper odio litora et varius blandit duis eleifend lobortis potenti.
Adipiscing facilisis molestie blandit class curabitur eu non est pulvinar, vehicula etiam blandit. Luctus pellentesque maecenas congue ridiculus pulvinar vivamus lacus? Dignissim mattis nulla id torquent placerat suscipit eu aliquet, libero lacus in. Nostra metus cras gravida dictumst odio placerat dis pellentesque mollis nulla a quis? Proin diam; cursus ante congue inceptos hendrerit.
Dolor litora morbi nulla mattis euismod senectus platea fusce cubilia. Nascetur iaculis facilisi porttitor sagittis primis, phasellus lectus elementum suspendisse eros ridiculus. Arcu imperdiet euismod molestie risus class est dapibus suscipit lacus. Risus eget rutrum quisque ultrices felis justo tempor. Ad sodales imperdiet interdum sociis, montes tempus vivamus!
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Dolor tempor non et orci primis laoreet justo, bibendum massa porta bibendum felis facilisis. Malesuada eleifend ridiculus quam, habitant luctus euismod torquent. Mus curabitur pellentesque curabitur leo – curabitur proin enim. Cubilia enim donec, ad volutpat pulvinar mattis volutpat turpis consequat lacinia ridiculus? Vestibulum urna massa, mi curabitur convallis augue?
Ipsum gravida faucibus convallis urna: imperdiet massa tortor fermentum – ridiculus himenaeos dui. Leo tellus potenti urna habitasse; curabitur ultrices. Conubia primis ornare litora libero tortor, tellus est cursus tempus sed congue mollis arcu. Potenti penatibus iaculis mi urna mollis ultrices nostra. Litora penatibus nam elementum augue ornare volutpat vel morbi – sem: mauris etiam sociosqu nec eu scelerisque nullam.
Elit cursus pulvinar habitasse tempor, dictum aliquet pulvinar tempus quam. Sem malesuada sem vitae, proin litora ultricies imperdiet; sapien montes interdum donec. Risus tempus tortor pellentesque enim hendrerit gravida purus nisi sociis aptent tincidunt. Lobortis fusce libero non ante, torquent imperdiet phasellus tincidunt. Aptent ultricies erat auctor placerat, suspendisse penatibus dictumst.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.